[PATCH] iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY even betterer

[Vladimir Oltean]

Hi,

On Thu, Dec 15, 2022 at 04:51:55PM +0000, Robin Murphy wrote:
> Although it's vanishingly unlikely that anyone would integrate an SMMU
> within a coherent interconnect without also making the pagetable walk
> interface coherent, the same effect happens if a coherent SMMU fails to
> advertise CTTW correctly. This turns out to be the case on some popular
> NXP SoCs, where VFIO started failing the IOMMU_CAP_CACHE_COHERENCY test,
> even though IOMMU_CACHE *was* previously achieving the desired effect
> anyway thanks to the underlying integration.
> 
> While those SoCs stand to gain some more general benefits from a
> firmware update to override CTTW correctly in DT/ACPI, it's also easy
> to work around this in Linux as well, to avoid imposing too much on
> affected users - since the upstream client devices *are* correctly
> marked as coherent, we can trivially infer their coherent paths through
> the SMMU as well.
> 
> Reported-by: Vladimir Oltean <vladimir.oltean at nxp.com>
> Fixes: df198b37e72c ("iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY better")
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> ---

Could someone please apply this patch?